An air-conditioning apparatus or a refrigerating and air-conditioning apparatus includes a compressor to be driven by an electric motor, e.g., a DC brushless motor. The DC brushless motor is subjected to PWM control performed by a drive control device including a converter and an inverter. Then, a capacity of the compressor is regulated in accordance with an air-conditioning load or the like. When the air-conditioning load is high, a PWM signal is controlled such that a large output voltage is applied. In a case of a light load state, the PWM signal is controlled such that a small output voltage is applied.
Various techniques have been proposed for the drive control of the above-mentioned electric motor through pulse-width modulation (see Patent Literatures 1 to 3). In Patent Literatures 1 and 2, there is disclosed that a carrier frequency to be used for the pulse-width modulation is varied in accordance with operating conditions to enable a stable operation. In Patent Literature 3, there is disclosed that a minimum value of a voltage value to be output is fixed or a minimum value of a dead time is changed based on detection of a DC current so as to set a minimum value of ON time of an output voltage, thereby enabling a stable operation.